Variable volume firing chamber

ABSTRACT

Apparatus for varying the volume of a firearm combustion chamber to alter the impulse so as to allow the firearm operator to select a level of impulse appropriate to the range and mode of firearm utilization. The firing chamber volume may be increased either by placing the chamber in communication with a sub-chamber or by enlarging the chamber in an axial direction by withdrawal of a portion of the breech section.

States atent 11 1 11 1 Goldin et al. May I, 1973 [5 1 VARIABLE VOLUME FIRING 3,380,344 4/1968 Bucklisch et a1 ..s9/14 R CHAMBER 1,864,374 6/1932 Romberg et a1. ..42/76 R 1,445,126 2/l923 Bergman.... ..89/] F [75] Inventors: Moms Gddm, Orange; 2,801,416 8/1957 Evans etal ....s9/1 R Downey, of Calm 3,326,082 6/1967 Johnson, Jr. et al. ..s9/1 F [73] Assignee: Hughes Tool Co., Aircraft Division,

C l Ci c lifl Primary ExaminerBenjamin A. Borchelt Assistant Examiner-C. T. Jordan [22] Flled' June 1970 Att0rneySmyth, Roston & Pavitt [21] App1.No.: 43,735

[57] ABSTRACT [52] U.S. Cl. ..89/14 R, 42/76 R, 89/1 F Apparatus for varying the volume of a firearm com- [51] Int. Cl ..F4lf 17/00, F4lc 21/00, F41c 21/12 bustion chamber to alter the impulse so as to allow the [58] Field Of Search ..42/76 R, 76 A; firearm perator to elect a level of impulse p- 1 539/14 1 1 R propriate to the range and mode of firearm utilization. The firing chamber volume may be increased either by References Cited placing the chamber in communication with a subchamber or by enlarging the chamber in an axial UNITED STATES PATENTS direction by withdrawal of a portion of the breech sec- 1,480,957 l/1924 Schneider ..89/l F tiOn. 3,359,856 12/1967 Grosschopf et a1 ..89/16 1,559,183 10/1925 Rimailho .189/l F 4 Claims, 8 Drawing Figures 1 n k\\\ k\\ Patented May 1, 1073 0 3,730,050

2 Sheets-Sheet 2 )x gm d firm/wa y:

VARIABLE VOLUME FIRING CHAMBER BACKGROUND OF THE INVENTION When a firearm is designed, the initial consideration must be the function which the firearm will be required to accomplish If the firearm is to have a relatively long effective range, the particular gun and ammunition combination must produce a relatively high level of energy or impulse so that the projectile will be capable of producing the desired effect at that range.

For example, a rifle with a range of 500 yards or more can be fired in a single shot or semi-automatic mode since the movement of the gun resulting from the impulse will not effect the accuracy of subsequent shots which occur at a later time. If such a gun were fired in a full automatic mode, the movement of the gun caused by the high level of impulse would cause the accuracy of subsequent shots to be extremely poor-if the gun could be controlled at all. On the other hand, if the rifle is to be used in operations in which an effective range of 200-300 yards is satisfactory, a much lower level of impulse is required and the gun can easily be controlled and fired in the full automatic mode.

In warfare situations, a long-range rifle is useful in large open areas having good visibility. In such an event, if an enemy is fired upon, a single-shot operation at a range of 500 yards is quite satisfactory. On the other hand, when the terrain consists of dense growth or other matter in which an enemy can easily hide and come within a short range before becoming exposed, it is highly desirable that a firearm be available which can be fired in the full automatic mode.

In the past, it has not been possible to provide a firearm which is efficient in the semi-automatic mode at long ranges and in the full automatic mode at short ranges, with a single type of cartridge.

Most of the guns which have been designed and used as combat firearms are essentially comprises between the two preferred types of firearms. Since it is logistically desirable to use a minimum number of cartridge types, combat firearms have often been designed in which the performance during semi-automatic, long range operation is less than optimal so as to insure that the same gun and cartridge can be used at close range in the full automatic mode.

The principles described above are not, however, limited to the rifle normally used by a foot soldier but are equally applicable to every firearm from the largest artillery piece to the smallest pistol.

In many present major artillery firearms, the effective range may be varied both by changing the angle of elevation of the barrel and by changing the impulse within the firing chamber. With respect to the latter, a maximum propellant powder charge is provided with each projectile. The impulse is varied by manually removing an approximate but predetermined amount of powder from the charge, and the remaining charge and the projectile are just then put into the firing chamber.

Since the amount of powder which is removed involves the exercising of human judgment every time a projectile is fired, it is also subject to error each time, making repeated accurate firing difficult. Additionally,

- if friendly troops are between the firearm and the target or are beyond the target, such an error, which alters the projectile travel distance, can cause disastrous consequences ifa short" or long" round is fired.

The gun crew safety is also compromised due to the necessity of opening loaded cartridge cases and handling loose gunpowder.

Other firearms, such as small mortars, are delivered with pulse charges and the angle of elevation can be altered or some powder removed to change the effective range of the firearm.

, In all firearms, therefore, it is highly desirable to be able to vary the impulse generated in the firing chamber so as to be able to more accurately control the firing range. This is also desirable since impulse variation ability will result in a much wider range of use for a specific firearm and type of projectile.

For example, a single firearm with impulse variation capability could be used on a fixed platform in high-impulse firing and in a light helicopter in low-impulse firing. In both of such applications, identical rounds would be fired but the aircraft would not be subjected to recoil forces which could possibly damage it or make it uncontrollable.

A variety of attempts have been made to produce systems which allow a variation of the impulse generated by the combustion of the powder charge. One such system has been provided having a series of chambers which are coaxial with the firing chamber, each one being successively larger than the last as the distance from the chamber is increased. In order to alter the impulse in such a firearm, a plurality of blocks is provided, each block sized so as to fit closely within one of the chambers. Thus, by altering the number of chambers which are open or closed to the firing chamber, the volume in which the charge is ignited and into which it can expand is altered.

With such a firearm, the impulse can be altered only after a long period of non-use since it would be impractical to expect the firearm to be opened while it is still hot in order to change the number of blocks in the chambers. Even if this could be accomplished, it is quite cumbersome since the blocks must always be conveniently placed relative to the firearm so that they could be changed quickly. This results in the possibility of the blocks being lost or misplaced and then being unavailable when they are needed.

Other firearms have been provided with a firing chamber venting system which may be opened to the atmosphere so that the gases can be released both through the bore of the barrel and the venting system. This has proven to be undesirable since the gas may escape in an area in which it can cause damage or produce harmful effects on those operating the firearm. Additionally, the escape of the gas through the venting system at the high pressures involved in powder combustion result in rather rapid erosion 'of the venting system, thereby requiring that it be replaced at relatively frequent intervals or that the firearm be discarded entirely.

An additional disadvantage of this type of impulse variation also occurs in that the system is relatively inefficient. In other words, it has been found that in order to produce even small changes in the impulse of the firearm, a large change in the quantity of powder required in the firing chamber must be made.

In the more recent past, it has been found possible to vary the impulse in stud-driving tools by allowing the gases in the 'firing chamber to expand into a subchamber which is open only to the firing chamber. The

gases are cooled slightly in this sub-chamber and then flow back through the connecting orifice and escape through the barrel. In such a system, the firing chamber and sub-chamber are connected by an orifice which extends entirely around the bore approximately at the point at which the firing chamber and barrel bore intersect. In other words, the barrel is floating" relative to the firing chamber. This is not unsatisfactory in such tools since the muzzle is normally positioned flush with the surface into which the stud is to be driven.

The variation of the impulse with which the stud is to be expelled from the tool allows the operator to take into account the type of material into which it is being driven.

It has not been readily apparent that the use of such a sub-chamber might possibly be applicable to weaponry since such tools are not used to propel studs great distances and also due to the fact that a firearm cannot generally be provided with a floating barrel since the far greater forces generated in a firearm firing chamber could cause the barrel to wobble and allow the projectile to miss its target. Additionally, this type of variable aperture would be highly susceptible to erosion, especially when it is opened only a small amount.

It is therefore an object of the present invention to provide a firearm which may be fired accurately within a wide range of projectile impulses, the precise level of which may be easily, quickly, and accurately selected.

SUMMARY OF THE INVENTION The present invention comprises a single firearm system which will allow the firearm to be used at the maximum practical level of efficiency at high-impulse firing, low-impulse firing, and at selectable intermediate impulse levels.

In the case of small arms, the invention allows maximum efficiency in both semi-automatic long range firing and full automatic close range firing. In the case of artillery and mortars, the invention precludes the heretofore necessary step of cutting the charge for each round. A gun or mortar can simply be set for the particular firing zone desired and the ammunition can be used without alteration. Additionally, when it is desired to install a high-impulse firearm in a vehicle having limited strength, such as a lightweight helicopter, the impulse may be reduced to within acceptable limits merely by the use of operator-controlled, temporary alteration of the firing chamber volume. In any case, the type of round which the firearm is designed to fire may be used in high-impulse or low-impulse firing, thereby reducing the logistical problems involved with ammunition delivery and storage.

The invention basically comprises a firearm having a firing chamber which may be varied in volume between volume limits (1) at which the available energy in the charge is most efficiently used and (2) larger volumes wherein the combustion efficiency is decreased with consequent reductions in impulse.

When the volume of the firing chamber is set at the most efficient ratio, a hand gun embodying these concepts will prove to be highly effective at long ranges in the semi-automatic mode; the impulse will be high and the impact force of the projectile will still be large at such ranges. On the other hand, when the firing chamber volume is increased, a less efficient use of the energy available from the combustion of the charge will occur and the impulse will be smaller; the decrease in impulse will cause the projectile to have an effective impact force at short ranges without causing the gun to move between shots, thereby resulting in accurate firing in the full automatic mode. In mortar and artillery applications, the concepts of the invention allow the firearm to be fired at less than maximum ranges without requiring manual variation of the propellant charge.

It is to be noted that the concepts of this invention are applicable to firearms which use any type of cartridge, including standard brass cartridges and caseless cartridges, and to nearly any type of firearm.

Other objects, advantages, modes, and embodiments of the invention will become obvious to those skilled in the art through reference to the detailed description and accompanying drawings which illustrate what are presently considered to be preferred embodiments of the best mode contemplated for utilizing the novel principles set forth in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 are partial sectional illustrations of a rifle, having a firing chamber with a large volume and low level of impulse when the' structure is in the position of FIG. 1 and a small volume and high level of impulse with the structure in the position of FIG. 2;

FIGS. 3 and 4 are partial sectional illustrations of an alternate embodiment of the concepts of the invention, with FIG. 3 corresponding to FIG. 1, and FIG. 4 corresponding to FIG. 2;

FIG. 5 is a partial cross sectional illustration of a valve which may be utilized to provide a variable volume expansion chamber;

FIG. 6 is a schematic-type illustration of a multiple valve system which allows an increase in the expansion volume in predetermined amounts and at predetermined stages during the operation of the system;

FIG. 7 is a simplified illustration of a mortar provided with a plurality of expansion chamber valves so as to allow an operator to select a zone of fire merely by opening a predetermined number of valves; and

FIG. 8 is a partial cross sectional illustration of the type of valve used on the mortars shown in FIG. 7, taken along a line VIII--VIII thereof.

DETAILED DESCRIPTION Referring now to the embodiment shown in FIGS. 1 and 2, there is illustrated a rifle barrel 11 having a bore 13 which communicates with a firing chamber 15 in a breech section 17. A firing pin 19 of any suitable type is positioned at the rear of the firing chamber 15 so as to ignite a charge Within the chamber 15 when the firing pin is actuated by the impact of a firing hammer (not shown).

An aperture 21 extending radially from the chamber 15 is in communication with a rotatable valve member 23 having a bore 25 therein. When a handle 27, which is fixedly attached to the valve member 23, is positioned as shown in FIG. 1, the aperture 21 forms a passage between the firing chamber 23'and the bore 25, thereby forming a sub-chamber to enlarge the effective volume of the firing chamber 15. When the handle is positioned as shown in FIG. 2, thereby causing rotation of the valve member 23 to the position shown, the bore 25 is removed from communication with the aperture 21 so that the firing chamber is maintained at its most efiicient volume.

Thus, when the valve is positioned as shown in FIG. 2, the rifle may be used effectively at long ranges in the semiautomatic mode. When the valve is positioned as shown in FIG. 1, the rifle will be effective at short ranges and the impulse will be low enough so that good accuracy may be obtained in the full automatic mode.

Referring now to the embodiment illustrated in FIGS. 3 and 4, a rifle barrel 29 having a bore 31 is suitably fastened to a breech section 33 having a firing chamber 35 therein. As shown in the figures, a fully telescoped caseless cartridge 37 is positioned within the chamber 35. Such a cartridge has been fully disclosed in the copending US. application Ser. No. 5,031, filed Jan. 22, 1970, now Pat. No. 3,687,077, and assigned to the assignee hereof.

A filter pin 39 is positioned at the rear end of the chamber 35 by any suitable means such as a tubular member 41 which may be fixed to the breech section of the rifle by a member 43. A volume adjustment tube 45 is concentrically mounted on the tubular member 41 and is effectively sealed thereagainst by a seal member 47. The outer surface of the volume adjustment tube is sealed to the wall of the firing chamber by a sealing means 49.

Rotation of a handle 51 between the positions shown in FIGS. 3 and 4 causes the volume adjustment tube 45 to move axially along the member 41 due to a linkage 53 which may be ofany desired type.

When the volume adjustment tube 45 is in the position shown in FIG. 3, the effective volume of the firing chamber 35 is increased by the amount of the displacement of the tube and a relatively low-impulse will occur when the firing pin 39 ignites the cartridge 37. When the tube is moved to the position shown in FIG. 4, the effective volume of the chamber 35 will be such as to produce maximum combustion efficiency with a very high level ofimpulse.

Referring now to FIG. 5, there is shown a breech or barrel section 51 having a firing chamber or bore 53 therein from which a passage 55 leads to an expansion volume 57. A valve member 59 having a sealing means 61 thereon is positioned within the volume 57 and, as illustrated, can be utilized to prevent communication between the passage 55 and volume 57 by being axially positioned within the volume so as to close off the outer end of the passage.

The valve member 59 is situated within a housing 63 so as to be rotatable relative thereto by means of a handle or knob 65. Rotation of the knob causes the valve to be moved into or out of the volume due to the further toward the right, increasing the size of the expansion volume, the impulse will be decreased still further. As has been previously stated, relatively small increases in the size of the expansion volume will produce significant decreases in the impulse generated and this type of infinitely variable expansion volume may be used to create extremely accurate impulse levels in such firearms for which this degree of accuracy is a requirement.

With reference now to FIG. 6, there is shown a rifle bore or firing chamber 71 having a first passage 73 and a second passage 75 in communication therewith. Passages 73 and 75 are situated so as to be selectively communicated to expansion volumes 77 and 79 respectively.

A valve 81 is situated so as to open and close the expansion volume 77 and avalve 83 performs a similar function for the expansion volume 79. Since these valves are identical, only the specific structure of the valve 81 will be described. As shown, the valve is provided with a first seating surface 85 and a second seating surface 87. These surfaces cooperate with valve seats 89 and 91, respectively, so that the surfaces 85 and 89 prevent communication between the passage 73 and volume 77 when the valve is closed and the surfaces 87 and 91 prevent communication between the volume 77 and the atmosphere when the valve is open.

Each valve is connected by an actuating rod 93 to a cam pin 95. The cam pin 95 associated with the valve 81 rides within a cam slot 97 and the cam pin 95 associated with the valve 93 rides within a cam slot 99, both slots being formed in a camming lever or plate 1 1 1.

A handle 113 attached to the camming lever is used to move the lever in either one of two directions designated by the arrow 1 15 so that the cooperation of the cam pins 95 with their respective cam slots will result in a sequential opening of the valves 81 and 83.

With a valve structure of this type, the rifle may be fired at a high-impulse level when the cam plate 11 1 is moved to the maximum clockwise position, as viewed in the drawing. When it is desired to fire the firearm at an intermediate impulse level, the cam plate may be rotated to the position illustrated so as to provide communication between the chamber 71 and the volume 77 as shown. On the other hand, when it is desired that low-impulse level firing be accomplished the cam plate may be moved to the maximum counterclockwise position, as viewed in the drawing so that both expansion volumes are in communication with the chamber 71.

Now with reference to the embodiment illustrated in FIG. 7, there is shown a mortar tube 121 which is positioned on a base plate 123 by means of a socket mounting 125. A plurality of valve-operated expansion volumes or chambers are formed in the wall of the mortar tube and communication between the firing chamber or bore and the expansion volumes may be controlled by the operator by means of selective actuation of levers 127 so as to control the exact impulse level at which the firearm is fired.

As shown in greater detail in FIG. 8, each lever 127, acting through a toggle linkage 129 and a connecting rod 131 serves to control a valve member 133 to prevent or allow communication between an expansion volume 135 and a passage 137 leading to a bore 139.

relative to the axis of the firing chamber. In this manner, the applicants have provided several embodiments of a new and improved concept in the firearms art which yields a true advance in that art. Many further modifications, alterations, and embodiments of these concepts will be obvious to those skilled in the art.

What is claimed as the invention is:

1. In a firearm having a firing chamber, a barrel, and means for firing a projectile in said firing chamber through said barrel, the improvement comprising:

means in said firearm for varying the impulse generated therein by the ignition of a cartridge in said firing chamber and the expulsion of a projectile through said barrel from a first relatively high impulse level suitable for effective, relatively long-range firing and a second, relatively low impulse level suitable for effective, relatively short-range firing, said impulse varying means comprising a passage in communication with said firing chamber, a valve means in said passage and including a first seating means and a second seating means, and means for moving said valve means along an axis of motion between a first position in which said firing chamber is in communication with said subchamber and a second position in which said firing chamber is prevented from communicating with said subchamber such that, when said valve means is in said first position, said first seating means prevents cartridge combustion gases from leaving said firing chamber and said subchamber except through said barrel and, when said valve means is in said second position, said second seating means prevents cartridge combustion gases from entering said subchamber.

2. In a firearm having a firing chamber, a barrel, and

' means for expelling a projectile in said firing chamber passage means intermediate said firing chamber and said expansion chambers,

valve means associated with each of said expansion chambers for opening and closing said passage means,

means associated with said valve means for preventing communication between said expansion chamber and the atmosphere except through said barrel and means or individually and selectively actuating said valve means to vary the total of the expansion chamber volumes between predetermined maximum and minimum volumes including cam means attached to each of said valve means and cam actuating means for sequentially actuating each of said valve means through said cam means as motion is imparted to said cam actuating means.

3. In a firearm having a firing chamber, a barrel, and means for firing a projectile in said firing chamber through said barrel, the improvement comprising:

means in the firearm for varying the impulse generated by the ignition of a cartridge in said firing chamber and the expulsion of a projectile through said barrel comprising means for supporting a firing pin at the rear of said firing chamber,

volume adjustment means located about said supporting means and forming a portion of the wall of said firing chamber, and

means for actuating said volume adjustment means to a plurality of positions relative to said firing pin.

4. A firearm comprising a combustion chamber,

an expansion chamber,

means for connecting said combustion chamber and said expansion chamber in gas flow communication, including a pair of valve seats therein,

valve means in said connecting means and movable between a first position against one ofsaid pair of valve seats wherein said combustion chamber and said expansion chamber are in gas flow communication and a second positioning against the other of said'pair of valve seats wherein said combustion chamber and said expansion chamber are shut off from gas flow communication, and

means for positively actuating and maintaining said valve means against at least one of said pair of valve seats. 

1. In a firearm having a firing chamber, a barrel, and means for firing a projectile in said firing chamber through said barrel, the improvement comprising: means in said firearm for varying the impulse generated therein by the ignition of a cartridge in said firing chamber and the expulsion of a projectile through said barrel from a first relatively high impulse level suitable for effective, relatively long-range firing and a second, relatively low impulse level suitable for effective, relatively short-range firing, said impulse varying means comprising a passage in communication with said firing chamber, a valve means in said passage and including a first seating means and a second seating means, and means for moving said valve means along an axis of motion between a first position in which said firing chamber is in communication with said subchamber and a second position in which said firing chamber is prevented from communicating with said subchamber such that, when said valve means is in said first position, said first seating means prevents cartridge combustion gases from leaving said firing chamber and said subchamber except through said barrel and, when said valve means is in said second position, said second seating means prevents cartridge combustion gases from entering said subchamber.
 2. In a firearm having a firing chamber, a barrel, and means for expelling a projectile in said firing chamber through said barrel, the improvement comprising a plurality of enclosed expansion chambers, means for selectively providing communication between said firing chamber and each of said expansion chambers comprising passage means intermediate said firing chamber and said expansion chambers, valve means associated with each of said expansion chambers for opening and closing said passage means, means associated with said valve means for preventing communication between said expansion chamber and the atmosphere except throUgh said barrel, and means for individually and selectively actuating said valve means to vary the total of the expansion chamber volumes between predetermined maximum and minimum volumes including cam means attached to each of said valve means and cam actuating means for sequentially actuating each of said valve means through said cam means as motion is imparted to said cam actuating means.
 3. In a firearm having a firing chamber, a barrel, and means for firing a projectile in said firing chamber through said barrel, the improvement comprising: means in the firearm for varying the impulse generated by the ignition of a cartridge in said firing chamber and the expulsion of a projectile through said barrel comprising means for supporting a firing pin at the rear of said firing chamber, volume adjustment means located about said supporting means and forming a portion of the wall of said firing chamber, and means for actuating said volume adjustment means to a plurality of positions relative to said firing pin.
 4. A firearm comprising a combustion chamber, an expansion chamber, means for connecting said combustion chamber and said expansion chamber in gas flow communication, including a pair of valve seats therein, valve means in said connecting means and movable between a first position against one of said pair of valve seats wherein said combustion chamber and said expansion chamber are in gas flow communication and a second positioning against the other of said pair of valve seats wherein said combustion chamber and said expansion chamber are shut off from gas flow communication, and means for positively actuating and maintaining said valve means against at least one of said pair of valve seats. 